The present invention relates generally to backup rings for high pressure seals used in an annular packing space between a first cylindrical member which reciprocates within a cylindrical bore of a second member, and more particularly, but not by way of limitation, to such backup rings for seals specifically designed for use in sealing a reciprocating plunger pump within a high pressure cylinder of an intensifier pump utilized for pumping fluids.
There are in the prior art various pressure intensifying systems where a larger working piston is reciprocated to provide a high pressure output through smaller high pressure pistons or plungers that reciprocate within high pressure cylinders.
These pressure intensifying systems are useful for a variety of purposes including waterjet cutting systems having cutting heads equipped with nozzles that direct high pressure and high velocity jets of water to cut, drill, and shape workpieces. For such processes, intensifiers are used to increase the pressure of supply water to pressures above 40,000 psi. Examples of high pressure intensifiers for producing a high velocity fluid jet stream are shown and described in U.S. Pat. Nos. 3,811,795 and 5,092,744, which patents are incorporated herein by reference. The high pressure water is delivered from the intensifier to the cutting head and discharged through nozzles as waterjets which cut workpieces.
In generating the high pressures required for waterjet machining operations, however, a very difficult sealing problem is encountered at the high pressure end between the reciprocating piston or plunger and the pressure cylinder wall, particularly when very high pressures are to be generated. Typically, O-rings are used to accomplish this seal. After repeated cycling of the piston or plunger within the high pressure cylinder, however, these seals tend to leak. This leaking problem is further exacerbated by deterioration problems with the seals encountered due to the hydraulic load from the high pressure fluid end of the pump. As a result, this leads to frequent repair of these component parts which is both costly from the standpoint of replacement parts, labor intensive maintenance, and lost production due to machine downtime.
The foregoing illustrates limitations known to exist in present high pressure hydraulic devices. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly a support for a seal of a pump is provided including the features more fully disclosed hereinafter.
According to the present invention, an improved support for a seal is provided in the form of a back-up ring that reduces or eliminates the gaps created between a pump plunger and a high pressure cylinder of a pump when the cylinder is pressurized. The support includes a back-up ring having opposed first and second faces with a wall thickness disposed between the faces. The back-up ring includes a frustro-conical concave surface on the first face and a frustro-conical convex surface on the second face. Also provided are a packing assembly including at least one back-up ring and a reciprocating pump incorporating the at least one back-up ring.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with accompanying drawing figures.